docs(meta): secure the cascade as the Phase-5 walkable-world mechanism (D-012 amendment)

Jeroen's gap catch: T-750 never stated that the seed-to-tile cascade is
also what determines the world where the player walks. Now connected in
one statement across three homes: D-012 amendment (the founding 'chunks
load/unload around the player' driver now concretely = the D-227/D-239
cascade; 3x3 chunk neighborhood minimum, coarser context self-provided by
D-255(f) function composition, Atlas interaction never a precondition,
byte-identical either way), the matching T-750 deliverable note (in
changelog), and a one-truth consumer note on Q-093 for the Phase-5 insert
minimap (design deferred, no independent map pipeline expected).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

governance/decisions/architecture.md

@@ -46,6 +46,7 @@ Technical foundation decisions that constrain implementation: engine, client-ser
 - **Rationale:** Same principle as D-010 (multiplayer architecture) - design for the future, build the simpler version now.
 - **Raised by:** Tyre (Technical Architect), endorsed by Team Leader.
 - **Amendment (2026-04-05):** The ~150×150 visual tile estimate is superseded by [D-094](#d-094-district-spatial-hierarchy--chunk-block-district-naming-and-sizes) (256×256 visual tiles per district, 4×4 blocks). D-094 explicitly amends this decision.
+- **Amendment (2026-07-24):** "The world generates as you explore" is now concretely the seed-to-tile cascade ([D-227](#d-227), [D-239](#d-239)): Phase-5 in-world streaming derives the chunk neighborhood around the player (minimum the 3×3 chunks needed to draw the scene; prefetch radius a tuning constant) via the **same derivation the Atlas ladder samples** ([D-255](#d-255)). Coarser-layer context is self-provided by function composition (D-255 (f), the cache-accelerated pure function) — **Atlas interaction is never a precondition**; a player arriving anywhere without ever opening the atlas gets the byte-identical world, and the step-canvas serving work's cache-hit==cache-miss determinism gate protects exactly this property. The Phase-4 epic (T-750) carries the matching deliverable note; the insert minimap (Q-093) is noted as a same-derivation consumer, design deferred to Phase 5.
 
 ### D-020: Engine and architecture selection — Godot client + Rust simulation via subprocess/IPC
 - **Date:** 2026-02-09

governance/questions/architecture.md

@@ -322,7 +322,7 @@ Technical foundation questions: engine, protocols, data structures, performance,
 ### Q-093: Tile-based exploration map in player insert (Google Maps for the implant)
 - **Status:** Open (high interest)
 - **Question:** Reference: MapTileProvider (https://github.com/AngryMeenky/MapTileProvider) — lazy-loading tile map provider. Concept: the player's insert has a map that works like Google Maps — pan, zoom, tile-based rendering. Server generates map tiles from ECS exploration data (what the player has seen). Explored areas show room layouts, corridors, points of interest. Unexplored areas are blank/fogged. Zoom levels: room detail → building → district → zone → station overview. Knowledge-graph-driven overlays: NPC last-known positions (if the player tracked them), quest markers, danger zones, faction territories. Map tiles are server-authoritative (can't see what you haven't explored) and cached on the client. The tile pyramid approach means the map scales to any world size without loading everything at once.
-- **Cross-reference:** Information boundary (D-011), insert/minimap UI, knowledge graph (D-041), T-732 (minimap ticket). See also [D-255](../decisions/architecture.md#d-255) (body-map-viewer stepped Atlas render architecture, 2026-07-24) — a different system (Phase-4 world-generation Atlas, not the player exploration insert), but its server-authoritative per-step data canvases, tagged-envelope carrier, and client cache tiers are shipped prior art for exactly the tile-pyramid/lazy-load/server-authoritative-cache architecture this question sketches.
+- **Cross-reference:** Information boundary (D-011), insert/minimap UI, knowledge graph (D-041), T-732 (minimap ticket). See also [D-255](../decisions/architecture.md#d-255) (body-map-viewer stepped Atlas render architecture, 2026-07-24) — a different system (Phase-4 world-generation Atlas, not the player exploration insert), but its server-authoritative per-step data canvases, tagged-envelope carrier, and client cache tiers are shipped prior art for exactly the tile-pyramid/lazy-load/server-authoritative-cache architecture this question sketches. One-truth note for Phase-5 scoping (D-012 amendment 2026-07-24): the natural expectation is that this map consumes the **same seed-to-tile derivation** as the walkable world and the Atlas — no independent map pipeline; recorded as a note here, binding design deferred to Phase 5.
 
 ---